The present invention is related broadly to the field of feed mechanisms for automatically feeding successive logs into a sawmill in which the logs are cut into cants and, subsequently, into lumber.
There has been much advantage realized lately in the lumber industry in the provision of "one pass" lumber forming operations in which a series of chipping heads are provided in combination with one or more saws to cut and chip successive logs in a single pass into prescribed size lumber and marketable wood chips. The problem associated with sawing and chipping systems is in the proper holding and feed of successive logs to the mechanism. Logs are not always straight along their lengths nor uniformly round. Thus, the problem of holding successive logs along a prescribed path for efficient sawing thereof is a difficult problem to overcome. Unless the successive logs are held rigidly, they may turn or twist slightly as they move through the chipping and sawing stations. Such movement binds the saw blades. If this movement is slight, the result is that the lumber formed will have a longitudinal twist and will therefore be of inferior grade. If the twist is more violent, the bind upon the saw blades can be sufficient to damage the blades and cause a shutdown of the entire processing area until the blade is replaced or repaired.
U.S. Pat. No. 3,627,005 to Morton et al issued Dec. 14, 1971 discloses a machine for cutting peeler cores or logs into studs and chips. This machine is used to manufacture chips and lumber from logs. Logs are fed in a single pass through four chipper heads which reduce the log to a rectangular piece of lumber or "cant". Downstream of the chipper heads are saws that cut the cant into a number of smaller pieces. Logs slide on upright legs of an inverted U-shaped channel and are centered by an overhead centering drive wheel. The particular shape of the drive wheel is utilized to center the successive logs on the channel slide. The wheel is adjustable to accommodate different size logs. Other drive mechanisms are provided in the form of overhead spiked wheels. Output elevation of the successive logs is not adjustable nor are there specific provisions made for crooked logs or logs having swelled butts or other irregularities along their lengths.
U.S. Pat. Nos. 3,457,974 and 3,313,329 granted July 29, 1969 and Apr. 11, 1967 respectively to L. A. Mitten disclose method and apparatus for production of stud lumber from logs of small diameter. This method and apparatus works primarily on logs from five to eight inches in diameter. It includes chippers that take a flat cut and also form two longitudinal grooves on opposite sides of the flats. Overhead "V-grooved" rolls are located on a press to center successive logs and hold them as they move through the machine. One chipping head is movable to enable production of a finished four sided cant of either four by four or four by six inches in cross sectional dimension.
U.S. Pat. No. 3,344,826 to L. A. Mitten granted on Oct. 3, 1967 discloses an apparatus for production of pulp chips and stud lumber from peeler cores. This machine is to be utilized again on small diameter logs (five and one half to six inches in diameter). Two cutter or chipper heads are shaped to form on half of the cross sectional shape of the finished cant. Two overhead "V" rolls center each log on a chain conveyor and lead it into the chipping heads.
U.S. Pat. No. 3,934,630 granted on Jan. 27, 1976 to R. R. Cockle discloses a method and apparatus for producing rough cut lumber. This apparatus is also used strictly on small diameter logs. The unit is portable for use in situ. Four chipper heads form successive logs into four sided cants and a two bladed circular saw then cuts the cant into three boards. Each log is held steady by longitudinal guide splines that are received in grooves that have been cut in the log ahead of the chipper heads. The successive logs are centered prior to the groove forming operation by spring loaded bars and rubber tires.
The present feed mechanism is distinguishable from the above cited prior patents. It includes a "rosser" that forms a smooth surface along a bottom side of each log as it moves through the feed mechanism. This smooth surface is firmly gripped by longitudinal working flight of a spiked chain conveyor. Thus, along with downward press rolls, the successive logs are held firmly against lateral twist. Also, the successive logs are held against undesirable lateral movement by adjustable side rolls. These rolls are located on opposite sides of the working flight and are spring biased to press inwardly at diametrically opposed contact points along the log as it moves from the feed mechanism. Another important distinguishing feature to note is that the present feed mechanism is vertically adjustable. The feed rolls and rosser along with the longitudinal conveyor are mounted to a vertically movable framework. This frame may be selectively adjusted up or down to determine the elevational position of the logs as they move toward the chipper and/or sawing stations of the associated mill. Thus, the feed will determine the depth of cut made by the bottom horizontal chipper or saw. This adjustment is functional in determining the most efficient cuts to make in relation to the diameter of the log being fed to the forming apparatus.